Trace A and B select the same waveform

Trace A and B select the same waveform

I am trying to read the phase shift in a series RC circuit. I am using the 2-channel scope, I connect Channel A across the source, and Channel B across the resistor. It all looks good, I see the two wave forms shifted by time. Now is where I have the problem... On the scope, I right-click the Channel 1 trace and "Select a Trace" and choose Channel A. I then I right-click the Channel 2 trace and "Select a Trace" and choose Channel B. What happens is that the Channel trace 1 jumps off the first waveform and ALSO selects Channel B so that they are both selecting the same waveform and I cannot get them to separate. No matter what I try, they both stay on the same waveform to I am unable to do T2-T1. I have attached a screenshot showing the issue.